There are many applications in which a plurality of threaded connectors, usually arranged spaced from each other along a circle, have to be tightened or loosened. Such applications are for instance abutting flanges of pipes in a pipeline which are connected by bolts extending through aligned bores in the flanges of the pipes, or covers of atomic reactors which have to be tightly connected by a plurality of bolts. Up to now such bolts have been individually tightened, which is of course quite a time-consuming task. While for some special applications apparatuses have already been provided by means of which several bolts or other threaded connectors could be tightened or loosened simultaneously, in such known apparatus a separate fluid-operated driving element has been used for tightening or loosening each bolt or any other threaded connector, and such apparatus is extremely complicated, heavy and expensive, so that the handling thereof is likewise difficult.